The isolation of K-99 outer membrane protein pili from E. coli cells is currently practiced using a procedure which involves heating the bacterial cells with urea in a phosphate buffered saline solution. The ultimate isolation of the desired K-99 pili is achieved after a very complex isolation procedure requiring about 10 days' duration. The instant invention describes an improved process for the heating shock treatment of E. coli cells and the isolation of the K-99 pili in just a few hours. The isolated pili have uses in the manufacture of vaccines.